Apparatus for making water vapour permeable polymer sheet materials

ABSTRACT

Coagulation apparatus for producing thick microporous polyurethane sheet material by passing a layer of polymer solvent composition beneath a close spaced plate with liquid non-solvent fed to the gap between the plate and the surface to produce controlled initiation of the coagulation.

United States Patent [191 Warwicker 5] Mar. 25, 1975 APPARATUS FORMAKING WATER [58] Field of Search 264/218, 41; 425/71, 101, VAPOURPERMEABLE POLYMER SHEET 425/ 103 MATERIALS [75] lnventor: Eric AlbertWarwicker, Kings [56] References C'ted Lynn, England UNITED STATESPATENTS 2,510,967 6/1950 Flanagan 425/223 X [73] Asslgnee' ggg LynnNorfolk 3,609,805 10/1971 Fritsch 425/71 [22] Filed: Feb. 5, 1973Primary Examiner-R. Spencer Annear Assistant ExaminerMark Rosenbaum [2]]Appl' 329A) Attorney, Agent, or Firm-Abner Sheffer Related US.Application Data [62] Division of Ser. No. 42,793, June 2, 1970, Pat.No. [57] ABSTRACT Coagulation apparatus for producing thick microporouspolyurethane sheet material by passing a layer of [30] Foreign Apphgnmnrnomy Data polymer solvent composition beneath a close spaced June 1969plate with liquid non-solvent fed to the gap between the plate and thesurface to produce controlled initia- 52 11.5. C1 425/71, 264/41,425/101, tion of the Coagulation 425/364, 425/387 R, 425/455 51 1m. (:1B29d 7/22 12 Clam, 2 Drawmg Figures PATENTEUHARZS'ISTS Nb 5 Wm BAPPARATUS FOR MAKING WATER VAPOUR PERMEABLE POLYMER SHEET MATERIALS Thisapplication is a division of my co-pending Application Ser. No. 42,793filed June 2, 1970, now US. Pat. No. 3,729,536.

The present invention relates to methods of making microporous polymermaterials particularly but not exclusively materials free from preformedfibrous sheet reinforcement and to apparatus for carrying out themethod.

The invention is concerned with microporous polymer materials which areproduced by coagulating layers of polymers extended with liquidvehicles, for example, polymer solutions, gels or colloidal dispersionswith liquid non solvents. It has been suggested that the non solvent canbe applied to the surface of the layer of polymer solutions as a vapour,but this is not feasible for relatively thick layers e.g., 0.5millimitres upwards, or as a spray but this produces an uneven surface.The more usual method is to pass the layer on a support with the supportuppermost into a bath of the liquid non solvent.

This presents considerable problems in conveying the material throughthe bath especially in a continuous process since the polymer layer mayrequire a substantial period of time e.g., of the order of /2 hourbefore the polymer surface can be conveyed around a roller without asurface blemish being produced. An object of this present invention isthe provision of a compact and simple plant for carrying out the processof the present application.

The applicants have observed that attempting to pass the layer on asupport with the layer uppermost into a bath of liquid non solventbrings a number of problems. Thus the passage of the material into thebath of liquid and plant vibrations tend to set up ripples in thesurface of the bath and these can often cause surface patterns whichhave an adverse effect on the appearance of the material and render itunsuitable for use as high grade man-made leather like material.

The present invention finds a particular application in the productionof relatively thick polymer layers free from preformed fibrous sheetreinforcement for example from 0.5 millimetres up to as thick as 5millimetres or more and especially to the production of layers having athickness making them suitable for use as shoe upper materials forexample 0.8 millimetres to 1.5 millimetres preferably 0.8 to 1.1millimetres for womens weight shoes and 1.1 to 2.5 millimetrespreferably 1.5 to 1.8 millimetres for mens weight shoes.

In order to produce such materials in vapour permeable or microporousform from a layer on a support of solutions of polymers for examplepolyurethanes, in organic hygroscopic or hydrophilic solvents, forexample N,N dimethylformamide, the said solutions containing microscopicwater soluble particles, for example ground sodium chloride, bycoagulation with liquid non solvents for example water or water solventblends, the layer when immersed support uppermost in the aqueoussolution needs to remain immersed for about V2 to 1 hour to achievecoagulation of the polymer to self supporting form when the finishedlayers are to be about 1.5 to 2 millimetres thick. Longer periods arerequired for thicker layers and vice versa.

At speeds of entry into the non solvent through an unstabilized surfacewith the polymer sheet uppermost or less than 10 to 15 feet per minutesurface patterns due to ripples are very likely to occur on the surfaceof the coagulated polymer layer. Until the material has been immersed innon solvent for at least /2 hour. it cannot be conveyed around a rollerwithout the material being damaged. The present invention enables lowspeeds for example 1 to 3, 5 or 10 feet per minute to be used resultingin shorter production lines and substantial savings in space and cheaperplant.

The applicants have discovered that many of these problems can beovercome if the layer of polymer ex tended with liquid vehicle isarranged uppermost on a support and liquid non solvent in continuousform applied thereto. This is carried out at least for long enough tocoagulate the immediate surface. The remainder of the-coagulation can becarried out in the same or similar way even by spraying or by immersionin the conventional manner.

The applicants have also discovered that this application of non-solventcan be particularly conveniently carried out if a layer of polymersolution on a support is passed through a gap or slot and the gap orslot is sufficiently narrow for a stabilized meniscus to be set upbetween the upper surface of the layer and the adjacent wall of the slotwhen liquid non-solvent is supplied therebetween. The surface ofthematerial can be coagulated in this way with a smooth surface and thecoagulation can be completed thereafter either by continued treatmentwith a thin layer of non-solvent held smoothly against the coagulatedsurface as by overlying spaced plates or trailing flexible sheets, or byimmersion of the layer in a conventional bath of non-solvent.

Moreover this enables the layer to be coagulated whilst supporteduppermost on a support, the support can thus easily be conveyed throughthe process and the conveying problems and the requirement for largetanks of non-solvent associated with upside down coag ulation can beavoided.

The present invention also enables much smaller volumes of non-solventto be used for the coagulation and attendant removal of the bulk of theliquid vehicle or solvent. This reduces the scale of operation neededfor solvent recovery, allows the composition of the nonsolvent liquid tobe more readily controlled, and makes it possible should it be desiredfor a wide range of non solvents such as alcohols glycols, ketones andother non solvent liquids other than pure water to be used includingthose containing dissolved solids having non solvent action such asinorganic salts for example ammonium compounds suchas ammonium nitrate.The smaller volumes required both reduce the capital cost of the nonsolvent and fire risks and other hazards.

Whilst the process and apparatus is particularly suited to theproduction of unreinforced microporous polymer layers its advantageswill also be obtained in the production of reinforced layers. Thus whena sheet of polymer extended with liquid vehicle" or polymer extendedwith liquid vehicle in sheet form" is referred to both unreinforced andreinforced polymer compositions are included within the term unlessotherwise stated. Thus the invention is applicable to the coagulation ofpolymer extended with liquid vehicle not only when the polymercomposition exists as a sin-- gle homogeneous layer but also when itexists as a number of superposed layers of varying compositions forexample varying in polymer, pigment. stabilizer or other componentnature or content. as also when the polymer composition forms a coatingon or is impregnated into reinforcing sheets for example of woven, nonwoven or knitted fibrous material and especially needle punched polymerimpregnated felts such as described in British Patent SpecificationsNos. 914,711 and 914,713.

Thus according to the present invention apparatus for coagulatingpolymer extended with a liquid vehicle in sheet form on a support whichmay be porous or non-porous comprises first means for evenly applyingliquid non-solvent in continuous form across the full width of the saidsheet at least to the free surface of the said sheet irrespective of theorientation of the said sheet on the support, and drive means arrangedto move the said sheet on the support past the said coagulating means.Preferably the support is arranged to have the sheet on its uppersurface and the coagulating means are arranged to establish a continuouslayer of liquid non-solvent across the full width of the sheet.Desirably the coagulating means are such that the upstream boundary ofthe layer of liquid non-solvent is substantially stabilized againstmovement. Thus the coagulating or first means may utilize the surfacetension of the liquid non-solvent to stabilize its upstream boundary.

Thus the apparatus desirably includes coagulating means for establishinga thin continuous layer of liquid non-solvent across a surface whilstthe said surface passes the coagulating means, the said thin layer ofliq uid having a stabilized upstream boundary in the sense of movementof the said surface, means for forming a layer of an initial mixture ona support the surface of the layer remote from the said supportcomprising the said surface, and means for passing the layer on thesupport past the said coagulating means so that the said layer of liquidnon-solvent is established and the said surface of the initial mixtureis coagulated.

The first or coagulating means may comprise a plate positioned inclose-spaced relationship to the free surface of the sheet so as to forma slot therebetween and means for supplying non-solvent so as to keepthe slot filled. The thickness of the slot is desirably such that whennon-solvent is supplied to the downstream end of the plate the surfacetension of the liquid establishes a meniscus, adjacent to the upstreamend of the plate, between the plate and the free surface of the sheet onthe support.

The coagulating means preferably comprise a strip or plate arrangedtransverse to the direction of travel of the support and adjustablyspaced from the surface of the support so that a slot can be producedsuch as to enable a meniscus to be set up in the gap between the stripor plate and the surface of the polymer layer remote from the support. Afurther plate is preferably arranged beneath the support. Thenon-solvent supply means preferably comprise porous tubes extendingacross the width of the plate. These are preferably placed above thedownstream end of the plate.

They are conveniently made of the sintered high density polyethyleneVYON (Trade Mark) material described above. The production of this typeof material is described in British Patent specifications Nos. 750,239and 953,359 the disclosures of which are incorporated herein byreference.

They have the advantage of filtering the non-solvent supply andproviding an even feed and are cheap and can thus be easily replaced.

As mentioned above in a preferred form of this aspect of the inventionthe thin layer of non-solvent is maintained on the surface of the layerof polymer on the support until the said layer of polymer issubstantially completely coagulated to self-supporting form.

This is preferably achieved by arranging the support to run over anelongated tray with spaced plates or sheets arranged over the supportand a non-solvent supply arranged to maintain the said thin layer ofnonsolvent in the gap between the said plates or sheets and the saidsurface of the polymer layer. The sheets may be freely floating on thelayer of non-solvent and may be merely secured at their upstream end.

The non-solvent may be provided at a number of stations spaced down thetray with drain slots across the tray prior to the next inlet station.The arrangement can then run on a countercurrent basis by feeding theoutflow from each stage to the inlet of the preceding upstream stage.This arrangement enables a controlled concentration gradient of solventand non-solvent to be set up, and controlled at any desired level.

This enables the procedures disclosed in British Patent SpecificationNo. 981,642 to be readily carried out. However, whilst these may bedesirable for certain systems of polymer extended with liquid vehicle asdisclosed in that document they are not essential to the satisfactorycoagulation of the polymer-removable filler-solvent pastes preferred foruse in the present invention.

The plate may be at a slight angle to the horizontal so that the supportpasses downwardly beneath the plate, the angle being such that themeniscus can be established merely by supplying non-solvent on to thepolymer surface adjacent to the downstream edge of the plate.

Preferably means are provided to maintain the free surface of the saidsheet at least wetted with non solvent until the polymer issubstantially completely coagulated.

These means may comprise at least one covering sheet positioned abovethe polymer layer downstream of the plate so as to establish andmaintain a thin film of non-solvent evenly over the surface of thepolymer layer.

The method and means by which the layer of non solvent is maintained canbe varied. Thus fine sprays or mists could be used to keep the surfacewet but care would have to be taken to ensure that the wetting was evenacross the full width of the layer and for its full length until fullycoagulated.

ln another form of the invention the apparatus comprises meanscontaining a body of liquid non solvent, means for introducing the sheeton the support into the body of liquid non solvent at a substantialangle to the horizontal, plate means arranged to extend above thesurface of the body of liquid non solvent so as to produce a slotbetween the free surface of the polymer sheet on the support and theplate, the slot being of such dimensions that in conjunction with theheight of the plate above the still surface of the body of liquid nonsolvent any ripples which are produced in the body of liquid as by thepassage of the support into it are dampened out at the meniscus producedadjacent to the top of the plate between the free surface of the polymersheet and the plate.

In a preferred form of the invention means are provided to maintain boththe free surface of the said sheet and the free surface of the saidsupport at least wetted with non solvent until the polymer issubstantially completely coagulated.

The polymer is preferably dissolved in solvent but the term polymerextended with liquid vehicle is intended to cover systems in which thepolymer is in emulsion, colloidal or gel conditions as well as those inwhich it can reasonably be described as being in solution. Suchcolloidal or gel conditions are conveniently achieved by addition ofnon-solvent to a polymer solution. Examples of this method are disclosedin British Patent Specifications Nos.- 914,711, 946,069 and 984,088.However, any method, such as addition of an electrolyte, as disclosed inBritish Patent Specification No. 1,126,060, which reduces the solubilityof the polymer in the solvent can be used to achieve a colloidal or gelcondition.

The disclosures of these four specifications are incorporated herein byreference.

The non-solvent is preferably removed, as by drying, subsequent to theremoval of the solvent, it merely being necessary that, whilst anysolvent remains such as could cause disadvantageous reduction inpermeability sufficient non-solvent remains to prevent this happeningfor example by using a non-solvent with a higher boiling point than thesolvent.

If the viscosity of the system is insufficient to enable sufficientlythick coatings to be formed it can be increased by cooling the mixtureor adding thickening agents or by other conventional means.

A high vapour permeability was mentioned above as being desirable inshoe uppers for certain uses. Whilst a degree of porosity can occur whena layer of a polymer solution is bathed with a non-solvent for thepolymer miscible with the solvent, the pores formed whilst impartingsome vapour permeability are liable to be not predictably or evenlydistributed and may vary widely in size depending on a wide range ofparameters.

Further details of this aspect are to be found in the above-mentionedparent application as are details of the polymers and solvents andremovable fillers which can be used. sufficient solvent and temperatureresistance to withstand the process conditions and also is such that thepolymer layer adheres to its surface at least sufficiently to produce aflat layer on the surface of the support.

The support can thus comprise woven, knitted or non-woven textilematerials, flexible polymer sheet materials and flexible metal materialssuch as wire gauze. The textile materials are preferably made frompolyester fibres though any other solvent resistant fibre could be used.

When woven supports having a regular array of holes are used the supportpreferably has the following characteristics. The support preferably hasa stiffness (as herein defined) in the transverse or weft direction inexcess oftSA) 0.6 and (8V2) 0.9 preferably 0.8 and 1.3 and especially1.8 and 2.2 whilst being flexible in the longitudinal direction, asupport area (as herein defined) in excess of 50%, preferably 60% andespecially 70 to 95% and at least 500 passages per square inch,preferably 1,000 and especially 5,000 to 10,000, providing communicationfrom face to face of the support.

Stiffness is measured using the three point beam loading method. Thespan of the sample between the two knife supports is 3.8 centimetres andthe load rate used is 10 millimetres per minute and is applieddownwardly to the centre of the sample. Stiffness (5%) is defined as theload in Kgs required to produce a A cen timetre deflection and stiffness(5 /2) is defined as the load in Kgs. required to produce a /2centrimetre deflection.

Support area is defined as the of the total area of the surface of thesupport which is occupied by the material of the support and is within0.5 millimetres of the surface. With woven fabrics there may be primaryand secondary support areas and the sum of these is the support area asdefined herein. Primary support is the area provided by the warp threads(and possibly also weft in a plain weave) at the highest points in thesurface and is the of the total area provided by such threads above aplane passing through their mid points at the highest points in thesurface. Secondary support is the of the total area less the primarysupport provided by all threads above a plane passing through the midpoints of the weft threads at their point of nearest.

approach to the surface.

Thus in general terms primary support except in plain weaves is providedby the warp threads and secondary support by the weft threads. In plainweaves weft and warp both contribute and there is no secondary support.

The support can be porous or non-porous but if it is nonporous thesurface is preferably treated as by roughening it to produce a surfacekey for the polymer layer. Whilst the process is applicable to theproduction of permanent coatings on supports, it finds particularapplication in the production of unsupported sheet materials and in thiscase the support must be one from which the coagulated polymer layer canreadily be stripped without being damaged.

This stripping stage may result in a desirable drawing out of the innersurface of the material imparting a smooth fibrous appearance to ithaving in certain cases marked resemblance to the flesh surface of aleather produced from a natural hide, thus obviating the need for a shoelining when the articles are used as shoe uppers.

One particular material, which is both self supporting and has a degreeof flexibility and gives a very good flesh surface appearance, is aporous liquid permeable sintered polymeric plastics material especiallyone made from high density polyethylene and preferably having an averagepore size of 50 microns or more broadly 25- to 100 microns as measuredby the method described in 8.5.5. 1752;1963 using it propyl alcohol.Such a material is sold under the name VYON (Trade Mark).

Preferably the support is such as to provide a key for the polymer sheetsuch that the force required to re move the sheet from'the support isbelow the breaking strength of the self-supporting sheet at the time atwhich the sheet is removed from the support, but in the range 50 to2,000/grams per centimetre width. especially to 1,400 grams percentimetre width.

The sheet can be removed immediately after coagulation or after beingleached when a filler is used or after being dried.

The degree of adhesion can be controlled by wetting the support beforethe layer is formed on it either with solvent or liquid vehicle or withnon-solvent liquids either pure non-solvent or non-solvent/solvcntblends having non-solvent action. Thus the support desirably is treatedso as to have an even non-solvent content prior to the applicationthereto of the sheet of polymer extended with liquid vehicle so as toensure even penetration of the support and that any coagulation causedby the non-solvent content of the belt is also even. The support maythus carry an amount of non solvent liquid prior to the application ofthe layer of polymer to it so as to ensure that in conjunction with thesurface properties of the support the layer of polymer adheres to thesupport without curling away from it but is still capable of beingstripped from the support without rupturing once the polymer has beencoagulated to selfsupporting form.

The support preferably carries 50% to 80% by weight based on its ownweight of the non-solvent liquid. The non-solvent liquid may comprise to40% of the liquid vehicle the balance being the liquid non-solvent.

Reference has been made to the polymer layer on the support being passedthrough a surface of liquid nonsolvent which surface is stabilizedagainst movement. The word through is not to be taken as excluding thecase where the surface of the polymer layer forms one boundary of thestabilized surface and indeed this is the most convenient way ofcarrying the invention into practice.

FIG. 1 shows a longitudinal cross section schematic diagram of apparatusin accordance with the invention,

FIG. 2 shows a longitudinal cross section of a simple continuous processembodiment of apparatus in accordance with the present invention.

THE APPARATUS SHOWN IN FIG. 1.

This consists of an endless conveyor belt 51 of woven polyester fabric 3feet wide passing around an idler roller 52 and a driven roller 53 in aclockwise direction.

The dry belt is about 1.5 millimetres thick, weighs 107 grams per squarefoot and is made from polyester multifilament fibre (TERYLENE TradeMark) in a close woven twill weave. It has a 0.2% stretch at pounds pullper inch width 1.2% stretch at 50 pounds and 6.6% stretch at 100 pounds.lts breaking point is at 327 pounds at which stage the stretch 21.7%.

These results were measured using an Instron tensile testing machine at1,000% extension per minute as described below. The belt is a thickdense but flexible material.

The upper part of the belt runs through a gently inclined tray 54 about40 feet long. At the upper end of the tray the belt passes through aslot 55 formed between parallel glass plates 56 and 57. The lower plate57 is about 2 /2 feet long and the upper plate 56 is about 6 inches longand is adjustably mounted so that the thickness of the slot 55 can bevaried. A spray 60 or tap connected to a supply of water or other liquidnon solvent is positioned just downstream from the upper plate 56. Fourcross bars 61 carrying trailing polyethylene sheets 62 about 6 feet longare positioned evenly across the tray the first one starting immediatelybelow the spray 60. A tank 63 to receive the liquid flowing off the endof the tray 54 is positioned below the roller 53. The apparatus alsocomprises a reactor vessel for preparing polyurethane in solution andpipework, storage tanks pumps and mixing apparatus for distributingmicroscopic salt particles, stabilizers and other processing aids evenlythrough the polymer solution to produce one or more pastes and thendelivering the pastes to one or more extrusion dies located adjacent tothe upper end of the tray 54.

The apparatus shown in FIG. 1 is provided with two 30 inches wideso-called coathanger extrusion heads 66 and 67 so that a single ordouble layer of paste can be formed on the belt as desired. The rate offeed of the paste to the heads is adjusted to give the required wetcoating thickness for example in the range 0.1 millimetres to 3.0millimetres for each layer e.g., 0.1 or 0.5 to 1.0 for the the top layerand 0.7 or 1.2 to 1.8 or 2.5 for the substrate layer. The head 66 willbe referred to as the substrate head and the head 67 will be referred toas the topcoat head.

The apparatus is used as follows. A polyurethane is formed in solutionin dimethylformamide from a polyester by reaction with a diol anddiisocyanate under an inert atmosphere as described in more detail inExam ple 1. The polyurethane solution containing approximately 30% byweight of resin solids is mixed with microscopic sodium chlorideparticles about 2 (e.g., or in the range 1.0 to 2.5 parts by weight perpart by weight of resin and with small amounts of stabilizers andpigment. This substrate paste is evenly mixed and deaired and fed to thedie 66 to produce a layer of about 0.070 inches (1.8 mm) wet thicknesson the belt 54. A top coat paste is formed in similar manner butcontains 3 (e.g., in the range 2.5 to 5 or 6)parts of sodium chlorideper part of resin and is fed to the die 67 to produce a layer of about0.030 inches (0.76 mm) wet thickness on top of the substrate layer. Thebelt contains 50% to 80% preferably about non-solvent liquid, e.g.,water, by weight just prior to the first head 66. The composition ofthis liquid is usually predominantly water but it may contain from say5% to 40% by weight of dimethylformamide and preferably 10% to 20% byweight. The layers on the belt are then passed at 1 foot per minutethrough the slot 55. Water at 5C to 60C in this case about 15C issupplied to the spray 60 at a rate sufficient to maintain the gapbetween the top surface of the paste layers and the underside of theplate 56 filled with liquid. This gap is arranged to be about 1 to 3millimetres, in this case l/l6 inch or 1.6 millimetres thick so that astable meniscus is set up at the upper end of the slot and a smoothcoagulated surface produced. In the steady state this liquid is observedby sampling at the centre of the slot to contain about 5% by weight ofN,N'-dimethylformamide. The water supply is sufficient to maintain theslot full of water and also maintain a film of water over the wholesurface of the paste layers for the full length of the tray.

In this arrangement the belt is stopped after 35 feet of paste have beenspread on the belt and the belt held on the tray with the water supplymaintained for at least 70 minutes to complete the coagulation of thepolymer to microporous self-supporting form. The wet selfsupportingsheet is then stripped from the belt and immersed for 2 hours in waterat 60C to reduce the chloride ion content to 1,000 milligrams per squaremetre or less thus removing substantially all the salt and substantiallyall the dimethylformamide. The material is then dried at 98C.

THE METHOD FOR USE WITH THE APPARATUS OF FIG. 1

The polyurethane polymers used were made in solution indimethylformamide from a polyester by reaction with a diol and adiisocyanate under an inert atmosphere.

The reaction was carried out in pure N,N-dimethy1- formamide 139 BritishGallons) using 130 parts of an anhydrous adipic acid/ethyleneglycol/butane 1:4 diol copolyester having a molecular weight of about2,000

dispersed microscopic salt particles was made by mixing 121.1 parts ofpolymer solution S9 with 35.4 parts of N,N-dimethylformamide 126.4 partsof finely divided sodium chloride and 22.8 parts ofa carbon black acidvalue less than 2 and a hydroxyl number of about pigment master batch.sold under the Trade Mark DESMOPHEN 2001 The resultant paste contained25% resin solids and y y and 28-38 Parts Of anhydrous butane 114 had aviscosity of 87,000 centipoise at 25C measured diol and 0.1022 parts ofdibutyl tin dilaurate, 108 parts on a B kfi ld viscometen 0f P pl ldiisocyanate Was The pigment master batch was made by dissolving inadded and the rnlxture cooled so as to keep the temper- 322 parts f N N'di th ]f id 2 4 parts f ature below 59f? Wh the a t as sl bst STABAXOL acarbodiimide stabilizer against hydrolycomplete addltional butane 1:4(.1101 was added to react Sis of the polyurethane 32 parts of CYASORBwith the remaining free isocyanate groups and the tem- 24, namely 2,2idihydroxy 4 methoxy benzophenohe, perature held abouto 50 l vlsfiosltywas a stabilizer against ultra violet ray degradation of the about POISBall TI'IIS fiddIIlOIlflI CIIOII WES I5 polyurethane and parts of lyparts. Fmally 4.7 parts of a 1:1 methanol/N l l-d1mem ki th l 3-6 5 di i-bm l-4 thylformamld? blend was added to react y hydroxyphenylpropionate] methane, an antioitident of free lsocyanale Sill] P TheVISCPSIIY at for the polyurethane, and stirring into this 8.0 parts of{111$ Stage of a Sample at 4 3 9 P0156, the Rajah Black carbon blackpigment and, then mixing in solids content was 30%, the intrinsicvlscosity was 1.04 3&8 parts of the polymer solution 5 described aboveand the Huggms slope consta nt k of the viscosity num- The Rajah Blackcarbon black pigment is made by P was Thls Solutlon be referred to asthe channel process by Columbian International and is Solunon I statedby them to have an average particle size of 0.02 A sample of solution S1was then diluted to 15% resin microns, a surface a e of 156 quare metresper gram, solids and cast in a flat glass reservoir. The solvent was ani] absorption to produce a fl id paste f 1 3 i]- p f Off Slowly Overseverfl houfs and finally lilitres per gram and to produce a stiff pasteof 1.23 milmore p y under Vacuum at 50 C to glve a Substanlilitres pergram, a carbon content of 95.2%, and a voltially solvent freetransparent film 0.2 millimetres m matter Content f 43% l The sodiumchloride was ground in a pin and disc The ultimate tensile Strength was544 g p r q a mill with air classification to separate out fines andrecentlmetl'e measured y the method described in turn oversize particlesfor regrinding. The sodium chloish Standard Specification N0. 3144/1958using an ride powder before dispersing in the polymer solution strontensile testing mach e- 7 typically had an average particle size of theorder of 10 The notch tear strength was 128 Kg/centimetre. to 20 micronsusually about 13 to 17 microns with a Table 1 gives the values ofcertain physical properties standard deviation of the order of i 10microns. This of other polymer solutions used in the Examples.measurement wasmade by sedimentation measure- TABLE I Ultimate ViscosityHuggin's tensile Notch tear Initial Solution poise at lntrinsic SlopeResin strength strength modulus (25%) Number 25C. Viscosity constantsolids 7c Kgs/cm2 Kg/cm. Kgs/cm2 S1 3900. 1.04 0.37 30 544 128 72 S21960 1.08 32 646 62 S3 2300 0.87 32 534 144 62 s4 2260 1.11 32 s5 30400.97 32.3 675 158 61- S6 2500 0.98 313 S7 3800 1.02 33.5 S8 2720 1.0831.8 727 153 82 S9 2240 1.13 32.2 S10 2680 0.86 32.2 627 137 S11 1.0629.4 628 147 62 S12 1620 1.0 32.5 507 I61 76 I The notch tear strengthwas measured on an Instron A stabilized tpe y ates9ptainia 92.91 11.

Lil

ments using a Photo-extinction Sedimentometer'manufactured by EvansElectroSelenium Ltd., Model No. 41 used in accordance with themanufacturers instructions based on papers by H. E. Rose in Engineeringof Mar. 31 and Apr. 14. l950, and Nature of 1952. Volume 169, page 287.

This apparatus consists of a chamber in which the solid whose particlesize is to be measured can be dis persed ultransonically in a liquid andits rate of settling measured optically. The change in transmission oflight by the dispersion with time is related to the particle sizes ofthe particles and the measurements of this change enable the averageparticle size to be calculated.

It will be appreciated that these sedimentometer experiments give anindication of the general order of particle size of the majority of theparticles.

Shadow photography of typical samples of the ground salt has indicatedthat the salt particles have random rough irregular shapes includingquite elongated shapes as well as more compact cube or block shapes.

The dispersions typically contain a few particles having a maximumdimension as large as 70 microns but substantially all of the particlesare less than 40 to 50 microns, and most are less than 25 to 30 micronsin maximum dimension and have dimensions in the range down to 1 micronor so though a few may be even smaller. The salt is also selected tohave a low moisture content so that it does not cake, for example lessthan 0.5% and especially in the range 0.2 0.4%. It may also have ananticaking agent added namely MICROCAL at about 1% by weight. MlCROCALis a very fine particle size coprecipitated lime and silicate anticakingagent sold by Joseph Crosfield and Sons Ltd. The mixing and millingconditions are preferably carried out at relative humidities less than70% at 25C and preferably at about 50%.

A substrate paste was made from a blend of solutions S1 and S2 and wasmixed with 1.78 parts per part of resin of microscopic sodium chlorideof particle size similar to that used in making the topcoat paste, and apigment master batch similar to that used for the topcoat paste so thatthe finished substrate paste contained 5 sures of 62 pounds per squareinch and 105 pounds per square inch respectively with a belt speed of 1foot per minute. The water supply to the spray 60 was mains water at15C.

The material had the following physical properties thickness 1.65millimetres; weight 748 grams per square metre; ultimate tensilestrength L 11.0, X 11.8 Kgs. per square centimetre, elongation at breakL 300%, X 365%; initial modulus (25% extension) L 3.2 Kg. percentimetre, X 2.8 Kg. per centimetre; notch tear strength L 5.3, X 4.8Kg. per centimetre; pore size 10.5 microns (maximum), 5.5 microns(average), hydrostatic head 106 millimetres of mercury and averagedensity (calculated) 0.45.

These physical properties were measured as described in Belgian Patentspecification No. 732,482.

Examples 2 to 6 These were carried out in the same manner as Example 1apart from the polymer solutions used and the fact that in Example 5distilled water instead of mains water was used as the non-solvent.Table 2 sets out the polymer solutions used, the viscosities of thepastes, the pump pressures to the extrusion heads, the belt speed andthe physical properties of the materials produced, and includes thevalues for Example 1 for comparison.

The units used in Example 1 are also used in the table.

TABLE 2.

Example 1 2 3 4 5 6 Substrate paste Polymer solution SZ/Sl S6/S5/S4S7/S3 S7 S7 57/58 Paste viscosity 1720 1880 1360 1620 1620 1720 Pumppressure psi 62 l 12 70 7O 71 Topcoat paste Polymer solutions S9 S8S7/S11/ S2/S10 S2/S10 S2/S10 Paste 870 1520 790 670 670 670 viscosityPump pressure psi 118 176 53 53 50 Belt speed 1 l 2 1 1 1 Productthickness 1.65 1.5.5 1.66 1.96 1.93 1.81

Weight 745 667 657 798 756 753 Ultimate L 11.0 9.3 9.2 11.0 10. 9.6

tensile strength X 11.8 8.8 8.1 11.7 11.3 10.6

Elongation L 300 278 313 318 309 291 at break X 365 300 318 340 330 312Initial L 3.2 2.7 2.3 3.1 3.0 3.0 Modulus X 2.3 2.6 2.2 3.2 3.1 3.3

25% extension Notch tear L 5.3 4.5 3.8 5.3 4.8 .4 strength X 4.8 4.4 4.15.5 5.4 54

Pure (Au) 5 5 5.1 5 1 size (max) 10 5 11.1 103 2 Continued Example 1 2 34 5 6 Hydrostatic head 106 95 93 Water vapour permeability 4740 47404060 Average 0.45 0.43 0.40 041 0.39 0.42

density (calculated) Water vapor permeability was measured by the methoddescribed in British Standard Specification No. 3177/1959, but at 37Cand a nominal humidity gradient of 100% relative humidity.

These materials are all flexible and have a handle and drape closelyresembling a high quality calf grain leather. They can easily be madewithout carbon black and post dyed or different pigments or dyes couldbe incorporated in the polymer pastes.

They can be given a variety of surface finishes to make them resemblenatural leather finishes for example they can be converted to suedes bybuffing or sanding and the surface which was in contact with the beltand carries an impression thereof can be rendered similar in appearanceto the flesh surface of natural leather by sanding. The surfaces canalso be embossed for example by using a patterned foil as disclosed inBritish Patent Specification No. 54377/67 (Case PP. 33) the disclosureof which is incorporated herein by reference.

A variety of surface modifying finishes can be applied to the top or topsurface of a single layer material for example to impart a grain leatherlike finish.

One very suitable finishing operation is a treatment of the uppersurface with fine droplets of a solvent and heating, in a manner topartially collapse the microporous structure along the surface and forma thin fused polyurethane skin thereon; materials so finished often havea series of tiny spaced depressions, partially lined with fusedpolyurethane material (e.g., about 2 to 15 microns in thickness), atsaid surface. Another suitable finishing treatment involves applying tothe upper surface of the microporous material a thin top coat, such asan aqueous emulsion of a suitable polymer (e.g., an alkyl acrylatepolymer or copolymer such as a copolymer of butylacrylate with some 15%of acrylonitrile and about 1-2% of itaconic acid, which can becrosslinked on heating by the inclusion of ureaformaldehyde condensationproduct in the emulsion, as is well known in the art); the amount ofsuch polymer may be insufficient to close the pores, or sufficient toprovide a very;v

without unduly decreasing its ability to transmit water vapour. The topcoat may be a continuous layer which solvent and cure (cross-link) themixture of these two resins.

The material could also be dyed with conventional dyes for polyurethanesfor example before the treatment with solvent spray or the applicationof the top coat or both.

In yet a further alternative form of colouring treatment a dye iscontained in the non-solvent in which the polymer is coagulated. The dyemay be an lrgacet dye as mentioned above and the non-solvent may be anaqueous alcoholic solution of the dye. Further details of the processand examples of other suitable dyes are disclosed in British PatentSpecification No. 20735/68 (PP. 37) the disclosure of which isincorporated. herein by reference.

These finished materials can be readily made into shoe uppers and thusinto shoes by conventional techniques.

THE APPARATUS SHOWN 1N FIG. 2

This consists of an endless conveyor belt 10 of woven polyester fabricas described for FIG. 1 passing around three rollers 12, 13 and 14 andover an inclined tray 11. The tray 11 is arranged beneath the upper partof the conveyor and supports it for a substantial part of its length.The upper end 16 of the tray is on the same level as the top of theuppermost 14 of the three rollers thus providing a horizontal upperstretch of conveyor belt. The lower end 17 of the tray terminates justbefore the lower roller 12 and an end roller 13 is lo 'cated at the samelevel as the roller 12 so that the lower part of the conveyor belt isheld in a horizontal plane. The rollers l2, l3 and 14 are arranged todrive the conveyor belt down the tray 11 around the end roller 12horizontally to and around the roller 13 up at a steep inclined angleand around the roller 14 and thence back to the top 16 of the tray 11.The lower part of the conveyor belt is arranged to be within a tank 20so that when liquid is placed in the tank the horizontal lower portionof the conveyor belt 10 will be beneath the surface ofliquid. The tank20 also contains rollers 21 and 22 each placed respectively just beforethe rollers 12 and 13 in the direction of travel of the conveyor belt10. A guide roller 23 and a dancing roller are located outside the tank20 together with a rewind reel 25 sup- 'ported on rollers 26 and 27,roller 26 being driven by a further roller 28.

A pair of calender rollers 30 and 31 are positioned between the rollers13 and 14 and are arranged to be capable of calendering the conveyorbelt to varying degrees.

A pair ofextrusion heads 35 and 36 are located at the upper portion 15of the conveyor 10 so as to be adapted to lay down superimposed layersof polymer paste on the conveyor belt. At the top end of the tray 11 aplate 40 is supported adjustably parallel to the tray 11 so as toprovide a slot of adjustable thickness but of substantially greaterdimension in the direction of motion of the conveyor than its thickness.The plates extend across the full width of the conveyor. Immediatelydownstream of the plate in the direction of motion of the conveyor thereis arranged a Vyon tube 42 to feed liquid on to the surface of the plate40 at its downstream edge. Immediately downstream of this Vyon tubethere is a further glass plate about eight feet long provided with aVyon feed tube 44 adjacent its upstream edge. Bars and trailing sheets46 as in the arrangement shown in FIG. 6 are spaced down the rest of thetray. Below the end of each sheet 46 the tray has a transverse drainslot 47. Immediately prior to each bar 45 but downstream of thepreceding drain slot there is located an inlet pipe 48. The drain liquidmay either be discarded from the slots 47 or feed back to the precedinginlet 48 acting in effect as a counter current.

Preferably pure water is fed in at the end of the tank 20 adjacent theroller 13 and the liquid fed in counter current from the end of the tankadjacent the roller 12 to the lower end of the tray 11. The water fedinto the tank is preferably at 40 to 80C and at the other end of thetank its temperature is about 30C and its N,N'-dimethylformamide contentabout 3% by weight. The outflow from the tank is fed to the tray 11 incounter current and the final outflow 47 from the tray 11 is arranged tocontain up to about 10% of dimethylformamide which is recovered in asolvent recovery plant. The outflow could easily be arranged to have ahigher solvent content but it has been observed that as the solventcontent increases in the initial coagulating liquid the coagulatedsurface tends to be less smooth and can take on a matt appearance.

Measuring means (not shown) are located between the rollers 14 and theextrusion heads 35 between the two extrusion heads 35 and 36 and betweenthe extrusion head 36 and the plate 40 so as to enable control of thethickness of the extruded materials to be achieved. This can be done bymeasuring either the thickness or the weight of the material passing themeasuring means.

The equipment described above can be used to produce a water vapourpermeable self-supporting sheet material as follows:

The conveyor belt 10 is set running at the desired speed, c.g., l to orpreferably 3 to 5 feet per minute, the tank is filled with liquid, forexample water, sprays 42 are supplied with liquid for example water, andthe pressure between the rollers 30 and 31 is adjusted to give thedesired moisture content in the conveyor belt 10. The take-up driveroller 28 is synchronized with the speed of the belt 10. The materialwhich it is wished to coagulate comprising polymer dissolved ordispersed as a colloid or gel in a water miscible'organic solvent is fedto one or both of the extrusion heads 35 and 36 depending on whether asingle layer film or a double layer film is to be produced. The rate offeed of polymer to the heads is adjusted to give the desired thicknessor thicknesses, for example in the range 0.3 millimeters to 3.0millimetres. The film carried on the conveyor belt 10 and adhering to itpasses between the plate 40 and the tray 11. The separation of the plate40 from the top surface of the extruded film is adjusted to be such thata stable meniscus of liquid is established at the upper end of the plate40. The film on the conveyor thus first comes into contact with thecoagulating liquid in a stabilised state and the surface is evenlycoagulated. With water, even coagulation is produced when this meniscusof A and preferably 1/16th inch or below in thickness. As thecoagulating liquid is absorbed into the film further fresh liquid passesup beneath the plate 40 to replenish the meniscus. The film surface isthus rapidly coagulated and coagulation of the rest of the layer orlayers is continued as the conveyor passes beneath the sprays 42 andthen under the further stabilised film of coagulating liquid provided bythe polyethylene sheet 44. This sheet minimises the production ofsurface irregularities which are observed to occur when it is not usedand the sprayed liquid is merely allowed to run down the surface of theconveyor under gravity. The at least partially coagulated film thenpasses round the roller 12 and beneath the surface of the liquid in thetank 20. It will be appreciated that the conveyor belt is now uppermostand the film is underneath it. At the rate mentioned above for theconveyor and with the dunk tank 50 feet long the film takes 35 minutesto pass from the roller 12 to the proximity of the roller 21. Withinthis time sufficient solvent has been displaced from the film for thepolymer to be in a self-supporting condition. The leading edge of thefilm can thus be detached from the conveyor and led round the roller 21and back through the tank for a further period of 35 minutes duringwhich a substantial proportion, if not all, of the solvent is displaced,depending on the thickness of the layer or layers. The film is then ledaround the roller 22 out of the tank 20 over the roller 23 under thedancing roller 24 which controls the tension in the self-supportinglayer between the rollers 26 and 27 and then on to the reel 25 in aclockwise direction under zero tension. The factors of film thickness,the nature of the solvent and coagulating liquid, the conveyor beltspeed and the temperature of the liquid in the tank 20 and the length ofthe tank 20 should preferably be selected to ensure that substantiallyall of the solvent is displaced from the polymer film but if outsidefactors make it desirable the process may be run so that some solventremains and this can easily be removed in a further treatment of theself-supporting sheet material with a solvent miscible non-solvent forthe polymer which may be the same as or different to the coagulatingliquid.

The actual mixture fed to the extrusion heads could vary within widelimits but the apparatus is particularly suitable for use in conjunctionwith the formulations disclosed in British Patent Specification No.1,122,804 and British Patent Specification Nos. 1608/67 (Case PP. 27).

In an alternative form of the invention the tray 11 is dispensed with asis the roller 12 and they are replaced by roller arrangements whichdirect the conveyor belt into the liquid in the tank 20 at asubstantially vertical angle. The plate 40 is supported parallel to thedirection of entry of the belt into the tank and its upstream edge isarranged to be at a height greater than the maximum ripple heightencountered in the tank when running the apparatus. This once moreresults in a stable meniscus being established which is automaticallyreplenished by surface tension from the body of the liquid in the tank.The length of the plate is adjusted to damp down the motion of theripples so that the meniscus is held sufficiently stable for a surfacefree from dunk lines to be produced.

The function of calender rollers 30 and 31 mentioned above will now bedescribed in more detail.

Their function is to control the amount of coagulating liquid retainedin the belt when the process is running continuously. It is necessary todo this in order to achieve a balance between the need for sufficientadhesion of the polymer supplied from the extrusion heads to prevent thelayers distorting when coagulated and the conflicting need to strip theself-supporting film from the conveyor belt at the roller 21. If toomuch coagulating liquid remains in the belt the adhesion of the extrudedfilm will be insufficient and the shrinkage produced by the initialcoagulation of the top surface of the film at the plate 40 may be suchas to cause the edges of the film to separate from the conveyor belt ordelaminate. If too little coagulating liquid remained in the belt, theadherence of the coagulated layer to the belt at the time it reaches theroller 21 could be too great and this could cause difficulties. Thuswhilst the layer will be self-supporting at this stage it will not yethave achieved the strength which it will have after further treatmentand the stripping stage at the roller 21 might even cause damage to thelayer.

The particular degree of moisture needed in the bolt as it approachesthe extrusion heads will vary depending upon the factors mentioned abovein connection with the amount of solvent likely to remain in the belt atthe end of its passage through the apparatus but a balance can be struckbetween too great and too slight adhesion by trial and error.

According to a further aspect of the invention a method of making awater vapour permeable polymer sheet material which comprisescoagulating at least one surface of a layer of polymer extended withliquid vehicle on a support is characterized in that the methodcomprises causing continuous relative movement be tween the layer on thesupport and at least two bodies of liquid non solvent the sheet beingtransferred from being in contact with one body to being in contact withanother by being lead around guide means in a manner such that its freesurface is held out of contact with the said guide means and isprevented from assuming a concave transverse configuration.

Desirably the contact with the bodies of liquid non solvent is carriedon for sufficient time to coagulate not only the surface of the layerbut also to coagulate the layer to a form in which it can be strippedfrom the support.

The guide means preferably comprises a large diameter cylindrical orconvex guide surface such as a roll. By large diameter is meant asurface having a radius which is many times e.g., 10 to 50 or more timeslonger than the thickness of the layer on the support.

The layer is preferably also supported as by guides stentors or grips insuch a way as to prevent it assuming a convex transverse configurationat least during its contact with the first said body of liquid andpreferably throughout the period from its initial contact with the firstbody of liquid up to the stage at which it can be stripped from thesupport without rupturing.

The first body of liquid can be estabished in accordance with the aspectof the invention which uses a close spaced plate described above andthis may be most convenient when only low speeds of operation e.g., upto l0 feet per minute are desired to be used. The second or subsequentbodies of liquid can be established in the same manner.

Alternatively the second body of liquid can be provided by a tank, orbath such as is described with reference to H6. 2.

Subsequent bodies of liquid if used could conveniently involve the trayand trailing sheet arrangements described with reference to FIG. 2 andwhilst the slot and plate entry arrangement might be a convenient way ofsealing the entry end of the tray to prevent non solvent spilling outother means such as idler rollers underneath the support or a smooth lipto the tray could be used.

Alternatively the first body of liquid can be provided by a tank or bathof liquid into which the layer on the support can be lead by beingpassed round guide means with the free surface of the paste away fromthe guide means so as to have the support uppermost in the tank.

As described above the support can then be held flat by stentors, gripsor other means.

The layer on the support would then pass out of the bath around furtherguide means and up andover a series of one or more trays as describedabove. The layer once coagulated could be stripped from the support.

The invention also extends to apparatus for coagulating polymer extendedwith liquid vehicle in sheet form on a support which may be porous ornon porous which comprises first means for applying a body of liquid nonsolvent at least to the free surface of the said sheet second means forapplying a separate body of liquid non solvent at least to the freesurface of the said sheet, drive means arranged to move the said sheeton the support past the said first and second means in the sequence andguide means for transferring the sheet on the support from the firstmeans to the second means in a manner such that the free surface of thelayer is held out of contact with the said guide means and is preventedfrom assuming a concave transverse configuration.

What I claim as my invention and desire to secure by Letters Patent is:

1. Apparatus for making a water vapor permeable polymer sheet materialwhich comprises means for forming a layer of coagulable polymercomposition at least 0.5mms thick, said layer having a free surface, andfor passing said layer through a body of liquid, with said free surfacein contact with said liquid, to coagulate said layer, characterised inthat up-stream of said body of liquid there are means having a solidboundary, spaced from said free surface so that a slot is left betweensaid boundary and said free surface and in that means are provided forsupplying coagulating liquid down-stream of said slot so as to maintaina body of said liquid on said free surface and to keep the slot filledwith said liquid and in that the thickness of the slot is such that whensaid liquid is supplied downstream its surface tension establishes ameniscus between said boundary and said free surface, the constructionand arrangement being such that said free surface first comes intocontact with said supplied liquid at said meniscus.

2. Apparatus as claimed in claim 1 in which said forming and passingmeans comprise a support. means for depositing said layer on saidsupport and means for driving the support to carry said layer past saidsolid boundary, and in which the means having a solid boundary comprisea wall in substantially parallel relationship to said support and closeto said free surface. said liquid supplying means being situated tosupply said liquid downstream of said wall to form a thin film of liquidbetween said wall and said free surface.

3. Apparatus as in claim 2 in which said wall and meniscus are situatedabove said free surface.

4. Apparatus as in claim 2, said support being porous and there beingmeans for supplying coagulating liquid to penetrate the pores of saidsupport.

5. Apparatus as in claim 4 in which said support is an endless belt.

6. Apparatus as in claim 5 in which there are means upstream of saiddepositing means for controlling the amount of coagulating liquid insaid belt.

7. Apparatus as in claim 3 in which said support is a porous endlessbelt, said driving means comprises means for driving said belt at acontinuous speed in one direction, and said solid boundary and said wallare provided by an adjustably arranged plate.

8 Apparatus asclaimed in claim 1 in which means are provided to maintainthe free surface of the said sheet at least wetted with non solventuntil the polymer is substantially completely coagulated.

9. Apparatus as claimed in claim 8 in which the said means comprise atleast one covering sheet positioned above the polymer sheet downstreamof the plate so as to establish a thin film of non solvent evenly overthe surface of the polymer sheet.

10. Apparatus as claimed in claim 1 comprising means containing a bodyof liquid non solvent, means for introducing the layer on the supportinto the body of liquid non solvent at a substantial angle to thehorizontal, plate means arranged to extend above the surface of the bodyof liquid non solvent so as to produce a slot between the free surfaceof the polymer layer on the support and the plate. the slot being ofsuch dimensions that in conjunction with the height of the plate abovethe still surface of the body of liquid non solvent any ripples whichare produced in the body of liquid as by the passage of the support intoit are dampended out at the meniscus produced adjacent to the top of theplate between the free surface of the polymer sheet and the plate.

11. Apparatus as claimed in claim 1 which means are provided to maintainboth the free surface of the said sheet and the free surface of the saidsupport at least wetted with non solvent until the polymer issubstantially completely coagulated.

12. Apparatus as in claim 1 in which the means having a solid boundarycomprises a plate having its surface in contact with said body ofliquid.

1. Apparatus for making a water vapor permeable polymer sheet materialwhich comprises means for forming a layer of coagulable polymercomposition at least 0.5mms thick, said layer having a free surface, andfor passing said layer through a body of liquid, with said free surfacein contact with said liquid, to coagulate said layer, characterised inthat up-stream of said body of liquid there are means having a solidboundary, spaced from said free surface so that a slot is left betweensaid boundary and said free surface and in that means are provided forsupplying coagulating liquid down-stream of said slot so as to maintaina body of said liquid on said free surface and to keep the slot filledwith said liquid and in that the thickness of the slot is such that whensaid liquid is supplied downstream its surface tension establishes ameniscus between said boundary and said free surface, the constructionand arrangement being such that said free surface first comes intocontact with said supplied liquid at said meniscus.
 2. Apparatus asclaimed in claim 1 in which said forming and passing means comprise asupport, means for depositing said layer on said support and means fordriving the support to carry said layer past said solid boundary, and inwhich the means having a solid boundary comprise a wall in substantiallyparallel relationship to said support and close to said free surface,said liquid supplying means being situated to supply said liquiddownstream of said wall to form a thin film of liquid between said walland said free surface.
 3. Apparatus as in claim 2 in which said wall andmeniscus are situated above said free surface.
 4. Apparatus as in claim2, said support being porous and there being means for supplyingcoagulating liquid to penetrate the pores of said support.
 5. Apparatusas in claim 4 in which said support is an endless belt.
 6. Apparatus asin claim 5 in which there are means upstream of said depositing meansfor controlling the amount of coagulating liquid in said belt. 7.Apparatus as in claim 3 in which said support is a porous endless belt,said driving means comprises means for driving said belt at a continuousspeed in one direction, and said solid boundary and said wall areprovided by an adjustably arranged plate.
 8. Apparatus as claimed inclaim 1 in which means are provided to maintain the free surface of thesaid sheet at least wetted with non solvent until the polymer issubstantially completely coagulated.
 9. Apparatus as claimed in claim 8in which the said means comprise at least one covering sheet positionedabove the polymer sheet downstream of the plate so as to establish athin film of non solvent evenly over the surface of the polymer sheet.10. Apparatus as claimed in claim 1 comprising means containing a bodyof liquid non solvent, means for introducing the layer on the supportinto the body of liquid non solvent at a substantial angle to thehorizontal, plate means arranged to extend above the surface of the bodyof liquid non solvent so as to produce a slot between the free surfaceof the polymer layer on the support and the plate, the slot being ofsuch dimensions that in conjunction with the height of the plate abovethe still surface of the body of liquid non solvent any ripples whichare produced in the body of liquid as by the passage of the support intoit are dampended out at the meniscus produced adjacent to the top of theplate between the free surface of the polymer sheet and the plate. 11.Apparatus as claimed in claim 1 which means are provided to maintainboth the free surface of the said sheet and the free surface of the saidsupport at least wetted with non solvent until the polymer issubstantially completely coagulated.
 12. Apparatus as in claim 1 inwhich the means having a solid boundary comprises a plate having itssurface in contact with said body of liquid.